Lexicon Pharmaceuticals, Inc. and Fox Chase Cancer CenterPublish Findings on Immune Deficiency

THE WOODLANDS, Texas, June 8 /PRNewswire-FirstCall/ -- Lexicon Pharmaceuticals, Inc. today announced the publication of new findings from a joint research project with scientists at Fox Chase Cancer Center in Philadelphia, PA. Together with David L. Wiest, Ph.D., Lexicon researchers have discovered a novel and surprising role for ribosomal protein L22 (Rpl22) in the development of T lymphocytes. These findings have been published in the June issue of the journal Immunity.

Dr. Wiest and scientists at Lexicon Pharmaceuticals discovered that deletion of the ubiquitously expressed Rpl22 gene resulted in the up-regulation of p53, a key tumor suppressor gene that triggers apoptosis and cell death. Further, it was determined that this up-regulation of p53 was responsible for blocking alpha-beta+ T cell development thereby creating an immune-deficient state.

"The connection between Rpl22 and the p53-mediated apoptosis pathway is very exciting," said Dr. David Wiest, Member, Basic Science Division at Fox Chase Cancer Center. "If research confirms our theories, Rpl22 may prove to be an important biomarker for certain T cell immune deficiency diseases and some types of lymphoid cancers."

Rpl22 is one of several proteins that comprise the large subunit of eukaryotic ribosomes, cellular complexes that are responsible for translating messenger RNA and assembling proteins. Although not-required for translation, Rpl22 may play a role in protein synthesis or macromolecular assembly that is important for some cell types, but not others.

"These findings could help us to further define the pathways involved in T lymphocyte development and regulation," said Dr. Tamas Oravecz, Lexicon's Vice President of Immunology and Oncology. "While Rp122 will likely prove difficult for development as a classic drug target, understanding its role could contribute significantly to its potential as a biomarker for disease."

About Lexicon

Lexicon is a biopharmaceutical company focused on the discovery and development of breakthrough treatments for human disease. Lexicon currently has clinical programs underway for such areas of major unmet medical need as irritable bowel syndrome and cognitive disorders. The company has used its proprietary gene knockout technology to discover more than 100 promising drug targets and create an extensive pipeline of clinical and preclinical programs in the therapeutic areas of diabetes and obesity, cardiovascular disease, psychiatric and neurological disorders, cancer, immune system disorders and ophthalmic disease. To advance the development and commercialization of its programs, Lexicon is working both independently and through collaborators including Bristol-Myers Squibb Company, Genentech, Inc., N.V. Organon and Takeda Pharmaceutical Company Limited. For additional information about Lexicon and its programs, please visit http://www.lexpharma.com.

Editor's Note: 1. The article, "Ablation of Ribosomal Protein L22 Selectively Impairs alpha-beta T Cell Development by Activation of a p53-Dependent Checkpoint" may be obtained with a subscription at http://www.immunity.com/content/current. 2. For more information on Dr. David Wiest, please visit Fox Chase Cancer Center's website at http://www.fccc.edu or Dr. Wiest's research page at http://www.fccc.edu/research/pid/wiest.

Safe Harbor Statement

This press release contains "forward-looking statements," including statements relating to Lexicon's growth and future operating results, discovery and development of products, strategic alliances and intellectual property, as well as other matters that are not historical facts or information. All forward-looking statements are based on management's current assumptions and expectations and involve risks, uncertainties and other important factors, specifically including those relating to Lexicon's ability to successfully conduct preclinical and clinical development of its potential drug candidates, advance additional candidates into preclinical and clinical development, obtain necessary regulatory approvals, achieve its operational objectives, obtain patent protection for its discoveries and establish strategic alliances, as well as additional factors relating to manufacturing, intellectual property rights, and the therapeutic or commercial value of its drug candidates, that may cause Lexicon's actual results to be materially different from any future results expressed or implied by such forward-looking statements. Information identifying such important factors is contained under "Factors Affecting Forward-Looking Statements" and "Risk Factors" in Lexicon's annual report on Form 10-K for the year ended December 31, 2006, as filed with the Securities and Exchange Commission. Lexicon undertakes no obligation to update or revise any such forward-looking statements, whether as a result of new information, future events or otherwise.

Lexicon Pharmaceuticals, Inc.

CONTACT: Bobbie Faulkner, Manager, Investor Relations of LexiconPharmaceuticals, Inc., +1-281-863-3503, bfaulkner@lexpharma.com

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